Lipoprotein fraction analysis is useful for estimating the risk for coronary artery disease and for assessing the effectiveness of cholesterol lowering therapy. The overall objective of this project is to improve the analytical performance of current lipoprotein assays and to potentially develop new lipoprotein tests with improved diagnostic accuracy. In the past year, we have collected a series of serum samples in the following 4 categories: (1) High HDL-C (>80 mg/dL) with cardiovascular disease (N=58), (1) High HDL-C (>80 mg/dL) with no cardiovascular disease (N=58), (1) Low HDL-C (<30 mg/dL) with cardiovascular disease (N=47), (1) Low HDL-C (<30 mg/dL) with no cardiovascular disease (N=58). All subjects have LDL-C<130 mg/dL and are on no lipid lowering medications. HDL is a cardioprotective risk factor and is usually measured by its cholesterol content (HDL-C). HDL, however, is composed many other constituents and exists in at least 12 different subfractions and some forms of HLD, such as oxidized HDL are believed to be dysfunctional. The specific goal of this study is, therefore, to determine whether some other parameter for measuring HDL besides HDL-C may better a predictor of cardiovascular disease. Using the above collected samples, we will perform a compositional analysis of HDL (cholesterol, cholesteryl esters, phospholipid, lipid hydroperoxides, apoA-I, apoA-II, and apoE). We will also determine HDL subfractions by gradient gel electrophoresis and by an ELISA for pre-beta HDL. Several functional parameters of HDL, such as LCAT activity, CETP activity, PLTP activity, MPO activity, paroxonase activity, and cholesterol efflux potential will be determined. Next the ability of these different parameters of HDL will be compared to HDL-C for predicting the presence of cardiovascular disease in both the high and low HDL groups.